Transformer torquer



Oct. 26, 1965 Filed Dec. 14, 1962 R. K. BRODERSEN TRANSFORMER TORQUER 2 Sheets-Sheet 1 ROLF K. BRODERSEN INVENTOR.

ATTORNEYS Oct. 26, 1965 K. BRODERSEN TRANSFORMER TORQUER 2 Sheets-Sheet 2 Filed Dec. 14, 1962 ROL F K. BRODERSEN INVENTOR.

A TTORNE YS United States Patent 3,214,717 TRANSFORMER TORQUER Rolf K. Brodersen, Orlando, Fla., assigncr to General Precision, Inc., Little Falls, NJ., a corporation of Delaware Filed Dec. 14, 1962, Ser. No. 244,676 4 Claims. (Cl. 336-135) The present invention relates to torquers for platforms, gyros, accelerometers and the like, and more particularly to an electromagnetic torquer having a plurality of constant reluctance air gaps.

In accordance with the present invention, a rotor and stator cooperate to provide a plurality of flux paths including uniform air gaps between the rotor and stator. The arrangement is such that the flux across the air gaps remains constant during angular displacement of the rotor relative to the stator. The torque is created when a current is passed through the conductors mounted on the rotor and extending through the air gaps. As long as the flux density B and the current 1 both have the same phase and frequency or are DC, the torque produced is proportional to the product Bi. Since the reluctance of the air gaps does not change when the rotor is angularly displaced, the device is free of reaction torque. In accordance with another important feature of the invention, the need for flexlead or pigtail connections to the rotor can be eliminated to eliminate the restraint they would otherwise exert against movement of the rotor. This is accomplished by energizing the rotor conductors extending through the air gaps by means of an air gap transformer having the primary windings thereof on the stator and the secondary windings on the rotor.

Accordingly it is one object of the invention to provide an improved electromagnetic torquer for platforms, gyroscopes, accelerometers and the like.

It is another object of the invention to provide an electromagnetic torquer of the type described which is free of reaction forces on the moving part of the torquer.

It is a further object of the invention to provide a torquer of the type described in which reaction forces are eliminated and in which no electrical connections such as fiexleads or pigtails are made to the moving part.

It is a still further object of the invention to provide a torquer of the type described having a stator and rotor with a plurality of air gaps therebetween, the reluctance of the air gaps remaining substantially constant when the rotor is angularly displaced to eliminate reaction forces on the rotor.

Other objects and features of novelty of the present invention will be specifically pointed out or will otherwise become apparent when referring, for a better understanding of the invention, to the following description taken in conjunction with the accompanying drawings, wherein;

FIG. 1 is a plan view of one embodiment of the present invention;

FIG. 2 is a plan view of another embodiment of the present invention; and

FIG. 3 is a perspective View of a simplified form of the embodiment illustrated in FIG. 2.

Referring to FIG. 1, a reaction-free torquer is illustrated which embodies features of the present invention. It comprises a ring-shaped stator 12 having a rotor 14 rotatably positioned therein. The rotor 14 has a plurality of poles which extend radially outward and cooperate with the stator 12 to define a plurality of air gaps between the rotor and stator. In this specific embodiment there are four equally spaced poles 16-22 each having a curved pole face. The rotor and inner surface of the ring-shaped stator 12 have the same center of curvature,

and therefore, the reluctance of the air gaps will remain constant when the rotor rotates about the center 24.

A conductor 26 is wound about the stator 12 in a manner to provide four primary windings 28-34 which produce magnetic flux along the paths indicated by the arrows in FIG. 1. A conductor 36 is wound about the rotor 14 to provide four interconnected torquing coils 38-44 wound about the poles 16-22, respectively. Terminals 46 and 48 are provided on the free ends of the conductor 36 to enable flexleads or pigtails to be connected thereto and alternate ones of the coils 38-44 are wound in opposite directions so as to cooperate with the flux across the air gaps through which they extend to produce either a clockwise or a counterclockwise torque depending upon the direction of current flow through the conductor 36.

As long as the flux density B across the air gaps and the current i in the conductor 36 have the same phase and frequency, or are D.C., the torque exerted on the rotor will be proportional to the product Bi. Further, because of the constant reluctance of the air gaps, it is apparent that no tangential reaction forces will be present in the air gaps. The radial magnetic forces can be controlled by tuning the stator coils 28-34 with series capacitors to magnetically center the rotor 14 if it is floated by a suitable flotation fluid or supported by air or gas bearings. For some applications, the rotor can be rotably supported within the stator 12 magnetically by increasing the magnitude of the radial forces across the air gaps. The magnetic centering or supporting of a rotor in this manner is familiar to those skilled in the art from the microsyn literature produced by the Massachusetts Institute of Technology.

From the foregoing, it is apparent that the torquer 10 will provide a very effective, reaction-free torquer for use with platforms, gyroscopes, accelerometers and the like. The rotor, of course, would be connected for rotation with the movable element, such as the platform or a spin motor of a gyroscope, and by maintaining it accurately centered, the reluctance across the air gaps will remain constant to eliminate reaction forces on the rotor tending to cause rotation.

Referring to FIG. 2, a torquer 50 is shown whichillus trates another embodiment of the invention. It com prises a ring-shaped stator 52 having a plurality of radially inwardly projecting poles 54-60. A ring-shaped rotor 62 is rotatably positioned within the stator and has the same center of rotation 64 as the curved pole faces of the poles so that the reluctance of the air gaps at each of the poles will remain constant when the rotor is angularly displaced. A pair of diametrically opposed fixed field coils 66 and 68 are wound about the stator between the poles 54 and and the poles 56 and 58, respectively, to produce the flux paths illustrated by the dotted and dashed arrows. A pair of control primary coils 70 and 72 are wound about the stator between the poles 54 and 56 and the poles 58 and 60, respectively, to produce the flux paths illustrated by the dashed arrows. A pair of control secondary coils 74 and 76 are wound about the rotor 62 inwardly of the control primary coils 70 and 72, respectively, and are connected in series with four torquer coils 78-84 wound about the rotor at each of the poles 54-60, respectively.

With this air gap transformer type of arrangement, the current for torquing the rotor 62 is supplied to the torquing coils 78-84 by the control secondary coils which are linked with and energized by the flux produced by the control primary coils 70 and 72. Thus no flexleads or pigtails are required an the restraint which these elements exert on the angular displacement of the rotor is eliminated. In addition, this is accomplished while maintaining the reluctance of the air gaps constant as in the embodiment of FIG. 1 so that no reaction torques are exerted on the rotor.

Referring to FIG. 3, a torquer 90 is shown which illustrates a simplified version of the torquer 50. It comprises a stator 92 having a rotor 94 rotatably positioned therein. The rotor has four radially projecting poles 96-102 which cooperate with the inner surface of the stator to provide the constant reluctance air gaps previously described. A single loop torquing coil 104 is mounted on the rotor 94 and comprises a pair of U-shaped end portions 106 and 108. fitted over the poles 98 and 102, respectively, and interconnected by rings 110 and 112 on opposite end faces of the rotor 94. The torquing coil 104 is made of a good electrically conductive, non-magnetic material, while the rotor and stator are made of non-conductive, magnetizable material.

A first conductor 114 is wound about the stator 92 in a manner to provide coils 116-122 to produce the flux path I as indicated by the dotted and dashed arrows when a potential E is applied across the ends of the conductor 114. A second conductor 124 is wound about the stator 92 in a manner to provide coils 126-132 which produce the fiu'X path I as indicated by the dashed arrows when a potential E is applied across the ends of the conductor 124. It will be observed that the flux I passesfrom the stator into the pole 100 and from the pole 96 back to the stator. This produces a current i flowing counterclockwise in the torquing coil as illustrated by the dashed arrows on the torquing coil. The torquing coil current i passes through the air gaps defined by the poles 98 and 102 across which the flux I extends. Thus a torque is exerted on the rotor which can be controlled by the control primary coil on stator 92. As in the embodiment of FIG. 2, this is accomplished without any flexlead or pigtail connections to the rotor and without any reaction forces acting on the rotor since the air gaps have a constant reluctance as the air gaps in the previous embodiments.

While it will be apparent that the embodiments of the invention herein disclosed are well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A torquer comprising a ring-shaped stator element, a ring-shaped rotor element concentric with said stator element, one of said elements having spaced poles thereon cooperating with the other element in a manner to define a plurality of circumferentially spaced air gaps therebetween, said air gaps having a substantially constant reluctance when said rotor element is angularly displaced, a torquing coil wound about said rotor element at each of said air gaps, a primary winding wound about said stator element between at least one adjacent pair of air gaps, and a secondary winding wound about said rotor element between said one pair .of air gaps and electrically connected to the torquing coils extending through said air gaps whereby when said primary coil is energized it will produce a magnetic flux extending across said one pair of air gaps to generate an induced current in said secondary winding and the torquing coils connected thereto to exert a torque on the rotor element.

2. A torquer comprising a ring-shaped stator element, a ring-shaped rotor element concentric with said stator, one

of said elements having spaced poles thereon cooperating with the other element in a manner to define four equally spaced air gaps therebetween, said air gaps having a substantially constant reluctance when said rotor element is angularly displaced, a first pair of coils wound about said stator element between one diametrically opposed pair of said air gaps, a pair of control primary coils wound about said stator element between the other diametrically opposed pair of said air gaps, a pair of control secondary coils wound about diametrically opposed portions of said rotor element in alignment with said control primary coils, and a torquing coil Wound about said rotor element at each of said air gaps, each of said torquing coils and control secondary coils being connected in series with one another whereby the first pair of coils and control primary coils will produce a magnetic flux in the stator and rotor elements extending across said air gaps and the rotor magnetic flux will generate an induced current in the secondary coils and the torquing coils to torque the rotor element.

3. A torquer comprising a stator element, a ring-shaped rotor element coaxially disposed with respect to said stator element, one of said elements having four spaced poles thereon cooperating with the other element in a manner to define four equally spaced air gaps therebetween, said air gaps having a substantially constant reluctance when the rotor element is angularly displaced, torquing coil means wound about a diameter of said rotor element in a plane defined by one diametrically opposed pair of said air gaps, winding means on said stator element for producing a magnetic flux in said stator and rotor elements extending across the other pair of diametrically opposed air gaps in a manner to generate an induced current in said torquing coil means, and additional winding means on said stator element for producing magnetic flux in the stator and rotor elements extending across said one pair of diametrically opposed air gaps in a manner to cooperate with the induced current in the portions of the torquing coil extending through said one pair of air gaps to exert a torquing force on the rotor element.

4. The invention as defined in claim 3 wherein said torquing coil means comprises a single loop of electrically conductive non-magnetic material having a pair of U- shaped end portions fitted over the periphery of said rotor element and interconnected by rings on the end faces of the rotor element.

References Cited by the Examiner UNITED STATES PATENTS 1/62 Kamm 336 X 5/63 Bolton 336 X 

1. A TORQUER COMPRISING A RING-SHAPED STATOR ELEMENT, A RING-SHAPED ROTOR ELEMENT CONCENTRIC WITH SAID STATOR ELEMENT, ONE OF SAID ELEMENTS HAVING SPACED POLES THEREON COOPERATING WITH THE OTHER ELEMENT IN A MANNER TO DEFINE A PLURALITY OF CIRCUMFERENTIALLY SPACED AIR GAPS THEREBETWEEN, SAID AIR GAPS HAVING A SUBSTANTIALLY CONSTANT RELUCTANCE WHEN SAID ROTOR ELEMENT IS ANGULARLY DISPLACED, A TORQUING COIL WOULD ABOUT SAID ROTOR ELEMENT AT EACH OF SAID AIR GAPS, A PRIMARY WINDING WOULD ABOUT SAID STATOR ELEMENT BETWEEN AT LEAST ONE ADJACENT PAIR OF AIR GAPS, AND A SECONDARY WINDING WOULD ABOUT SAID ROTOR ELEMENT BETWEEN SAID ONE PAIR OF AIR GAPS AND ELECTRICALLY CONNECTED TO THE TORQUING COILS EXTENDING THROUGH SAID AIR GAPS WHEREBY WHEN SAID PRIMARY COIL IS ENERGIZED SAID AIR GAPS WHEREBY WHEN SAID PRIMARY COIL IS ENERGIZED IT WILL AIR GAPS TO GENERATE AN INDUCED CURRENT IN SAID SECONDARY WINDING AND THE TORQUING COILS CONNECTED THERETO TO EXERT A TORQUE ON THE ROTOR ELEMENT. 